Fix FOR UPDATE OF with explicit schema (knex#5053)

When the _tableNames helper was written there were multiple methods
hitting it, but they've since been merged into the single _lockingClause
method. Given that the only really interesting thing it was doing was
prepending the schema name--which is the incorrect behavior this commit
fixes--it didn't seem worth keeping at this point.

I'm not sure you'd say `.withSchema('public')` in a real query but it
lets me exercise the behavior in question without having to learn enough
about knex's test environment to stand up a discrete schema. I suppose
it's plausible that a reasonable maintainer would go "hm that's silly
and redundant" and inadvertently remove coverage for this bug, though.

lib/dialects/postgres/query/pg-querycompiler.js

@@ -197,29 +197,12 @@ class QueryCompiler_PG extends QueryCompiler {
     }
   }
 
-  // Join array of table names and apply default schema.
-  _tableNames(tables) {
-    const schemaName = this.single.schema;
-    const sql = [];
-
-    for (let i = 0; i < tables.length; i++) {
-      let tableName = tables[i];
-
-      if (tableName) {
-        if (schemaName) {
-          tableName = `${schemaName}.${tableName}`;
-        }
-        sql.push(this.formatter.wrap(tableName));
-      }
-    }
-
-    return sql.join(', ');
-  }
-
   _lockingClause(lockMode) {
     const tables = this.single.lockTables || [];
 
-    return lockMode + (tables.length ? ' of ' + this._tableNames(tables) : '');
+    return lockMode + (tables.length
+      ? ' of ' + tables.filter(Boolean).map(table => this.formatter.wrap(table)).join(', ')
+      : '');
   }
 
   _groupOrder(item, type) {

test/integration2/query/select/selects.spec.js

@@ -993,7 +993,7 @@ describe('Selects', function () {
         try {
           await knex.transaction((trx) => {
             // select all from two test tables and lock only one table
-            return trx('test_default_table')
+            return trx.withSchema('public').from('test_default_table')
               .innerJoin(
                 'test_default_table2',
                 'test_default_table.tinyint',
@@ -1010,6 +1010,7 @@ describe('Selects', function () {
               });
           });
         } catch (err) {
+          console.log(err.message);
           expect(err.message).to.be.contain(
             'Defined query timeout of 100ms exceeded when running query'
           );